Method of manufacturing shear fingers for sickle bars

ABSTRACT

Pointed shear fingers are formed, preferably in multiples, from a flat metal plate which is blanked out to the required outline. The blank is formed in a die which offsets the projecting finger portions and simultaneously creates a convexity on the bottom surface bordered by angled edges or bevels, the forming also producing a concavity in the top of each finger, leaving a flat V-shaped marginal portion which is ground in a single operation to provide shearing edges in conjunction with the formed bevels of the bottom side. Shear fingers are separated by clean-out recesses which are formed in the blanking operation.

United States Patent Haban METHOD OF MANUFACTURING SHEAR FINGERS FOR SICKLE BARS 1151 3,682,021 14 1 Aug. 8, 1972 [57] ABSTRACT Pointed shear fingers are formed, preferably in multiples, from a flat metal plate which is blanked out to the required outline. The blank is formed in a die which offsets the projecting finger portions and simultaneously creates a convexity on the bottom surface bordered by angled edges or bevels, the forming also producing a concavity in the top of each finger, leaving a flat V-shaped marginal portion which is ground in a single operation to provide shearing edges in conjunction with the formed bevels of the bottom side. Shear fingers are separated by clean-out recesses which are formed in the blanking operation.

2 Claim, 8 Drawing Figures PATENTED B 1912 V 3.682.021

'SHEET 1 OF 2 INVENTOR Z? 50 JOSEPH HABAN hW/KWZ ATTORNEYS PATENTEmus 8 I972 3.682.021

sum 2 or 2 1 HI fl ,3 X M 1 JO s E l-i THOARBAN f// BY ATTORNEY METHOD OF MANUFACTURING SHEAR FINGERS FOR SICKLE BARS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention pertains to shear fingers, often referred to as guards, which are used in sickle bar mowers.

2. Description of the Prior Art Heretofore some shear finger elements have been formed in two pieces, one part comprising a soft iron casting or forging which included a mounting portion to lock up against the fixed bar of the assembly. The soft iron casting also included an integral projecting portion to form a support for a ledger plate or blade which had to be riveted or otherwise secured to the projection. The ledger plates or blades, in the type of conventional construction, were made of high carbon material so that they could be heat treated, and the edges of the top surface of blade had to be specially machined at an angle, and the entire bottom surface of the blade had to be ground to produce the opposed shearing edges. There was a great deal of labor involved in the above procedure which increased the expense.

Some shear fingers have been one-piece forgings, but here the shearing edges had to be separately machined to provide bevels and then ground on the other side. This type of construction was also very expensive. In the conventional arrangements, because of the methods employed, the shear fingers were usually manufactured in singles.

SUMMARY OF THE INVENTION The present invention provides a novel method of manufacturing shear fingers which eliminates the separately formedledger plate or blade, the method providing for the forming of specially shaped fingers in a forming die in such a manner that there is a flat V- shaped marginal portion on the top of each finger which can be ground in a single operation to provide shearing edges in conjunction with bevels on the underside of the blade which are produced simultaneously with the forming operation without any special machina general object of the invention is to provide an improved method of manufacturing shear fingers.

A further object of the invention is to provide a method of manufacturing shear fingers by steps which include a stamping operation followed by a forming operation, thus providing, without additional machining, much closer tolerances than has heretofore been possible in prior methods where the major portion of the shear finger was a forging or a casting.

A further object of the invention is to provide a method of manufacturing shear fingers which makes it possible to provide a shear finger element of any selected length having any desired number of shear fingers thereon.

A further object of the invention is to provide a shear finger element wherein the shear fingers are separated by clean-out recesses which are formed in the blanking operation.

Other objects of the invention are to provide sheer finger elements which are simple in construction, inexpensive to manufacture, efficient in operation, and well adapted for the purposes described.

With the above and other objects in view, the invention consists of the improved shear fingers for sickle bars and method of manufacturing the same, and all of its parts, combinations, and steps, as set forth in the claims, and all equivalents thereof.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawings, illustrating one complete embodiment of the preferred form of the invention, in which the same reference numerals designate the same parts in all of the views:

FIG. 1 is a plan view of a portion of the blank for fonning the shear fingers;

FIG. 2 is a plan view of a completed shear finger;

FIG. 3 is an end view thereof;

FIG. 4 is a sectional view taken on the line 4-4 of FIG. 2;

FIG. 5 is a sectional view taken on the line 5-5 of FIG. 2;

FIG. 6 is a perspective view showing a fragment of the top side of a sickle bar assembly;

FIG. 7 is a perspective view showing a fragment of a sickle bar assembly, looking principally at the opposite side from FIG. 6; and

FIG. 8 is an elevational view, partially diagrammatic, of the die forming apparatus, showing a blank about to be formed.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly to the drawings, the improved shear finger elements are preferably manufactured from a flat plate of medium carbon steel (C-l045). In order to effect economy in manufacture it is preferred to form the shear fingers in multiples such as the doubles illustrated in FIG. 1, and to arrange to produce rows of elements with interfitting sets of fingers from a single strip of flat material. In FIG. 1 the numeral 20 designates an element with a mounting portion 16 carrying a pair of shear fingers 21 as cut from one side of a strip, and the numeral 20a another element in reverse position, so that the finger projections 21 on one side are interfitting with the finger projections 21a from the other side. The blanks 20 with the sets of fingers are cut by being passed through a conventional blanking die which blanks them out to the shape shown at 20 or 20a and simultaneously pierces the holes 18 and 19, the material between the interfitting fingers being discarded. The blanks are then preferably heated and fed into a forming die having a punch portion 10 and a die portion 1 l as shown in FIG. 8 and formed to the shape shown in FIGS. 2-5, inclusive. The forming die offsets the finger portions 21, as is clear from FIG. 3, there being a shoulder 30 at each offset. The central portion of the bottom of each finger portion is rendered convex in the forming operation as at 22 (FIG. 4) and simultaneously the forming die produces the beveled edges 23 as shown in FIG. 4, no special machining being needed for the bevels. At the same time a concavity 24 is produced in the top side, which concavity is bordered by flat edge and tip portions 25 arranged in V-shape in plan view as in FIG. 2. The material is also offset around the holes 18 as at 17 (FIG. 3). The concavity 24 creates relief between the flat margins 25, separating the two flat surfaces.

These flat surfaces 25 are then ground in a single grinding operation to produce the shearing edges 26 in conjunction with the bevels 23 which were produced solely by the forming operation. The grinding may be done on the flat face of a rotating stone. No grinding on the bottom face is required. In addition, forming of the angled portions 23 in the forming die creates a built-in roughness at the edges 26 which is somewhat helpful in the shearing operation as it tends to hold fine grasses while they are being sheared so that they do not slip out.

Each of the formed elements 20, immediately after forming, is then heat treated to harden the finger areas 21, by quenching in a quenching medium to a hardness of RC50-55.

The concavo-convex portion of each finger adds substantial strength and makes it possible to provide sufficiently strong fingers from a blank as thin as'O.l793 inch.

The improved shear finger elements are rigidly mounted on the sickle bar assembly by means of nuts and bolts 33 which pass through the assembly in the usual manner as shown in FIGS. 6 and 7. The movable knife is constructed in the conventional manner and comprises a plurality of V-shaped blades 27 connected together by a knife-back bar 28 which moves within the space 29 inwardly of the shoulders 30 at the inner ends of the offset shear fingers. Hold-down clips 31 are bolted to the assembly and serve to maintain the movable blades in shearing contact with the fixed shear fingers to maintain the relationship. It is to be noted that the hold-down clips are relatively long with respect to conventional practice, overlapping at least two blades, and with this arrangement uniform clearances between the upper and lower knives are more accurately maintained. Each hold-down clip has a large central opening 32 for clearance of portions of the clippings.

The sickle bar of FIGS. 6 and 7 will be otherwise supported and operated in the same manner disclosed in my US. Pat. No. 3,364,666, dated Oct. 9, 1964.

With the improved method of the present invention it is obvious that shear fingers can be manufactured more economically than with methods which require casting or forging operations, as such castings or forgings have required additional machining on both the top and bottom surfaces of the fingers. With the present invention the novel forming method makes it possible to maintain closer tolerances than has hereto fore been practical in forging or casting methods. In addition, with the present method of procedure, any desired number of shear fingers may be formed integral with a single element, with the latter having any selected length. This feature is particularly useful for small sickle bars where, with the present method, all of the shear fingers may be readily formed integrally as a single unit.

I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

What I claim is:

1. A method of manufacturing a shear finger element having a mounting portion with a projecting finger portion comprising the steps of forming a relatively shall cnc the ntral rtio onl of hen er six; 0 sai t g er por t i on so mat sa id coi icavity is '5'?- dered by flat marginal portions inwardly of the outline of the finger, simultaneously forming the lower side of said finger with a corresponding convexity which is bordered by marginal portions, and simultaneously forming the marginal portions of the blank to provide bevels on the lower side which merge with the flat marginal portions on the top side to produce shearing edges in conjunction with the formed bevels.

2.'A method of manufacturing a shear finger element as claimed in claim lincluding the step of first stamping the element from a flat metal blank and, thereafter, forming the blank in a die to offset the finger portion from the plane of the mounting portion and to produce the central concavity in the finger portion and to form the marginal edges to provide the bevels on the lower side. 

1. A method of manufacturing a shear finger element having a mounting portion with a projecting finger portion comprising the steps of forming a relatively shallow concavity in the central portion only of the upper side of said finger portion so that said concavity is bordered by flat marginal portions inwardly of the outline of the finger, simultaneously forming the lower side of said finger with a corresponding convexity which is bordered by marginal portions, and simultaneously forming the marginal portions of the blank to provide bevels on the lower side which merge with the flat marginal portions on the top side to produce shearing edges in conjunction with the formed bevels.
 2. A method of manufacturing a shear finger element as claimed in claim 1 including the step of first stamping the element from a flat metal blank and, thereafter, forming the blank in a die to offset the finger portion from the plane of the mounting portion and to produce the central concavity in the finger portion and to form the marginal edges to provide the bevels on the lower side. 